This invention relates in general to universal joint assemblies and in particular to an improved structure for a thrust washer for use between a bearing cup and a trunnion in a universal joint assembly.
Universal joints are well known devices which provide a driving connection between two members adapted to rotate about non-aligned axes of rotation. Universal joints are widely used between rotatable drive shaft sections in vehicle drive train systems. A typical universal joint includes a cross having a central body portion with four cylindrical trunnions extending outwardly therefrom. The trunnions are oriented in a single plane and extend at right angles relative to one another. A hollow cylindrical bearing cup having a cylindrical side wall and a circular end wall is mounted on the end of each of the trunnions. A plurality of bearings, such as needle bearings or roller bearings, are provided between the trunnion and the associated bearing cup to permit relative rotational movement therebetween. The bearing cups which are mounted on a first opposed pair of the trunnions can be connected to a first end yoke secured to an end of a first drive shaft section, while the bearing cups mounted on a second opposed pair of the trunnions can be connected to a second end yoke secured to an end of a second drive shaft section.
When the bearing cups are mounted on the opposed pair of trunnions, the end walls of the bearing cups are disposed adjacent to the axially outer ends of the trunnions and bearings. If the end walls of the bearing cups are fit tightly against the axially outer ends of the trunnions and bearings, friction between the surfaces during operation of the universal joint can generate heat and cause premature wear. If the bearing cups are fit loosely on the trunnions, the cross and trunnions can move back and forth within the opposed bearing cups during operation of the universal joint. This may create imbalance of the universal joint and generate undesirable noise and vibrations. Consequently, it is known to position thrust washers between the end walls of the bearing cups and the axially outer ends of the trunnions and bearings.
In the past, such thrust washers have been manufactured from a single annular piece of material having a first portion which engaged the axially outer end of the trunnion and a second portion which engaged the axially outer ends of the bearings. This structure performs well for most applications of universal joint assemblies. However, problems can occur when the universal joint assemblies are used in high speed, high angle, and low torque applications. In these situations,, the trunnion may become angled relative to the bearing cup and apply uneven pressure against the first portion of the thrust washer. When this occurs, one side of the first portion of the thrust washer is forced against the bearing cup, while the other side moves away from the bearing cup. Because the first and second portions of the thrust washer are formed as a single piece of material, the corresponding side of the second portion of the thrust washer also moves away from the bearing cup. When the bearings engage this side of the thrust washer, the thrust washer is subjected to significant wear and may eventually break apart. This can cause early failure of the bearing cup assembly. Accordingly, it would be desirable to provide a thrust washer for a universal joint assembly that avoids the potential problems occurring in high speed, high angle, and low torque applications.